update to the latest es6-collections 3.0
update to the latest es6-collections 3.0

I however remove the `is` property definition, as we already have a more
complete polyfill for `Object.is`

rlugojr/melonJS,melonjs/melonJS,rlugojr/melonJS,melonjs/melonJS,rlugojr/melonJS